BillBax - GK Studio Extreme

Started by Elantric, January 31, 2017, 11:45:17 AM

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"There's no-one left alive, it must be a draw"  Peter Gabriel 1973


Thanks Elantric for posting this topic. Bit of a tough one GK Extreme...

* Audiophile GK3 separate strings, and an improved audio specification compared to a GK3 with GP-10's usb separate string outputs.
* Drives a line-input at 1V, and no need for any gain.
* Low separate string total-harmonic-distortion at 1V or +2dB.
* Separate string signal-to-noise ratio is around -105dB, but can go as low as -108dB.  Note:  A signal-to-noise ratios is difficult to measure below -100dB, and reading fluctuations are common. Separate string maximum output calibration is critical.
* Diecast aluminium enclosure keeps EMI to a minimum.
* GK Extreme can be powered at +/-15V, as most op-amps perform better at 15VDC.

* Bulky multicore phonos/d-sub cable set required for separate strings out.  If you want to re-amp a v-synth symultaneously, a second custom multicore cable set is needed.
* Battery powered.  Most people do not like using battery operated devices, even though batteries can add precious dBs to a signal-to-noise ratio.
* Studio use only, due to the cumbersome multicore cable set.
* High component costs normally about fifty British pounds.

Adding Gumbo's 'military specification' 13-pin socket might be the beginning of a GK3 audiophile preamp. With six top panel DIP switches, dropping the preamps higher output, enabling regular 13-pin v-synth use.  A GK-Volume (pin-8) and UP/DOWN switches are also essential additions.  Does this sound like another GK3?

I am a big fan of OPA2134 as a gain-stage for the GK3 sensor, as the days of using NE5532 op-amp are long gone. Having said that, there are many untested state-of-the-art high-end op-amps available.  The new MUSES range by NJR spring to mind, and the mighty LME49990 op-amp is another one my shopping list.


GK Extreme 2008

3D Model with d/subs

GK3 Versus GK Extreme.  Signal-to-noise-ratio.

Signal-to-noise-ratio - one string.




"Does this sound like another GK3?"

.....let's try for at least GK4A..   ::)

...thinks: 'Time to get back into bunker...'   :-X
Read slower!!!   ....I'm typing as fast as I can...


Hi All,

Happy to report my GK buffer preamp works exceptionally well with a GP10 and GR55. Wouldn't dream of using a GK buffer preamp on stage, although in the studio, the need for hi-end GK and v-synth recording is critical. I have 12 years of research material with the GK buffer preamp, and would be delighted to post more findings should they be of interest.


GK Extreme 2007 - Fully screened audio from GK3 sensor to v-synth.

Dedicated custom length multicore cable with six phonos, individual 100% screen coverage, resistor phantom-power mod for pin-8/v-synth PCM voices, and one 1/4 jack plug for guitar grounding.

GK buffer vs GK3 noise-floor in GP10 sensitivity settings (all strings).
Spectrum analyser reports GK3 noise-floor @ -85dB and -92dB with GK Extreme buffer preamp.

The key to an improved GK3 preamp performance mainly hinges on GP10s generous input sensitivity headroom - typically +8dB past the last LCD segment.


Wow interesting. 

I wonder if the cable from the guitar to the "wart" such as it is could be extended so the wart could be mounted on the strap and connected/disconnected to the hex pickup?  Convertible mode if you follow my line of thinking?
My music projects online at

GK Devices:  Roland VG-99, Boss GP-10, Boss SY-1000.


Hi philjynx,

No not really, I've worked on dozens of GK3 sensors. Of course, you only get two or three goes taking one apart before the brittle aluminium fold-overs fail. After that, it's 3mm cut black tape around once or twice in two places.   


QuoteI wonder if the cable from the guitar to the "wart" such as it is could be extended so the wart could be mounted on the strap and connected/disconnected to the hex pickup?  Convertible mode if you follow my line of thinking?

A possible wind up question.  The extreme preamp is all about hi-end recording with separate strings and very little else. You must have understood this reading through all the blurb posted on this topic? 

GK Buffer preamp into a GP10 with six Engineer Filters and Gate inserts. The screen capture shows a modelled GP10 Strat noise-floor. Mind boggling, a real strat has a noise-floor of about -70dB, give or take a few dB.  -102dB with a modelled strat sounds like warp 11.


Can that also function as a low noise breakout for the hex pickup by using and connecting 6 male phono to 1/4" plug cables?


QuoteCan that also function as a low noise breakout for the hex pickup by using and connecting 6 male phono to 1/4" plug cables?

Hi Chris,

Yes, the GK buffer was originally intended as a hi-end breakout box and GK preamp in one - taking out the need for a breakout box hub, and dramatically improving a GK3's audio specification. You only need to replace the cables 13-pin plug with 1/4 inch jacks for breakout box operation, plus you have 1-Volt separate string outputs that needs very little daw line input-gain.

GK3 VS GK Buffer separate string noise-floor.

Recently finding out the GK buffer can be used with a GP10/GR55, has made me think about serious recording, and can't imagine going back to a GK3.


GK Extreme VS GK3 recording in VST raw.
In cubase recording and listening tests, GK buffer is about +5dB compared to a GK3. And the noise-floor is around -2dB lower (Effectively 7dB quieter overall). If you record externally with a GP10, you are not limited to a daw sequencers input-channel record clipping, and therefore a perceived audio improvement is much greater. 


Hi Everyone,

Thought you might like to hear the difference between my GK buffer preamp and GK3.

These .wav 16-bit files are from the VST audio pool, and there is no audio processing or tampering etc. Suggest you listen on a decent pair of headphones or studio monitors. Also playing them on a media player might induce some limiting or 'ducking'.

Just to refresh ones audio memory, the first of the three is an original strat middle pickup.
The guitar part is repetitive and articulated. It sounds ok, and just what you would expect from a raw strat middle pickup.

GK3 GP10 Strat model middle pickup. Sounds tonally similar to the original, although the top-end is a little brittle. Low-end below 200Hz sounds thin and lacks intimacy.

GK buffer with GP10 Strat model middle pickup. A perceived +5dB average level increase, with an improved bass-end response. I can only described the top-end as having pleasant twinkles, and overall the audio is much more intimate compared to a GK3.

Thanks for listening,



Hi All,

Something for the weekend :D

Currently working on a new GK Extreme plugboard circuit, and opamps under test are LMH6629, OPA1602, OPA1611, LT1115 and the new MUSES8832 by JRC. The research goal is a GK3 sensor buffer preamp with an all strings dynamic-range of 100dB. Individual string dynamic-range is expected to be around 110dB.

Original GK Extreme buffer preamp simulator circuit 2007 1/6th. Minus a few components.



Hi everyone,

A louder Roland GK3 performs better, and quieter playing strengths are not lost in v-guitar background noise.




Hi all,

Did anyone see the spectrum analyzer shots in my recent GK3 vs GK Extreme youtube demo?  The A/B animated gif comparison shows how impressive noise-floor figures can be achieved following basic audio design principles.


1. GK3 sensor screen housing grounded = -1dB
2. Dual 9V battery psu = -3dB with audio psu ripple @ 50Hz = -7dB.
3. OPA1656 fet-input opamp for GK3 sensor signals = -3dB
4. +13dB true line-level string signal outputs.
5. Fully screened GK preamp in a diecast case = -???dB
6. Through-hole audio grade low-noise capacitors & resistors = -???dB
7. Fully screened GK 13-pin multi-core cable = -???dB
8. Lower v-guitar unit input sensitivity settings = -13dB compared to GK3 (generally). An Extreme preamp input requires 60 sens setting for medium playing strengths, while GK3 requires 90-100.  GK Extreme heavy solos and riffs require a sens setting of about 20. GK Extreme string signal noise-floor is around -105dB 8)

Line-level GK3 & GK Extreme string signals with medium playing strength:

GK3 = -15dB. Very poor and noisy.
GK Extreme = -2dB. Excellent.

There's lots more... and I didn't even mention improved audio punch ;) 
Thanks for viewing.